The present invention generally relates to an arrangement for a partial stiffening of a covering of a folding top, and more particularly, to an arrangement adapted to stiffen surface regions of a folding-top covering which have an arcuate contour.
A stiffening of this type is disclosed by German Patent Specification 3,818,616 wherein an essentially plane length zone in a rear region of the roof surface is supported by two tension belts. For this purpose, the two tension belts are stretched between the bow tube of a main bow and a virtually straight middle region of a corner bow. With the folding top closed, the two tension belts bear on the inner face of the folding-top covering virtually over their entire tensioning length.
In addition to their supporting function, the two tension belts of the above-noted patent serve the purpose of retaining the corner bow, connected to the fabric-holding bar via wire cables, in the desired installation position in the last phase of the closing movement of the top which is accompanied by a pivoting back of the fabric-holding bar. When the folding top is closed, the corner bow is fixed in its installation position by the oppositely directed pulling forces of the wire cables under the tension belts.
Furthermore, lateral roof frames of a folding-top structure according to German Patent Specification 3,818,616, in conformity with the folding-top structure of German Patent Specification 3,724,532, consists of slender flat iron bars which make it possible to fold the folding-top structure more compactly. However, this design of the lateral roof frame necessarily entails the disadvantage that they can scarcely make any contribution to stabilizing the lateral roof contour by a shaping support of the folding-top covering spanning it.
In this difficult region of the roof surface, therefore, the folding-top fabric has to be drawn into the desired roof contour of arcuate cross section solely by longitudinal tensioning forces in the folding-top fabric, its particular path being predetermined by the arcuate contour of the roof-top flank and by the arcuate contour of the corner region of the main bow. However, it is virtually impossible to execute this procedure especially because of the associated extreme tensile stress exerted on the folding-top fabric, since the aim is to achieve as smooth a folding-top structure as possible and as uniform a tension distribution in the folding-top covering as possible.
Thus, an object on which the present invention is based is to improve a partial stiffening of a folding-top covering,to the effect that it can be used for stiffening surface regions of the folding-top covering which have an arcuate contour.
The solution, according to preferred embodiments of the present invention, for achieving this object and other objects, results from providing a tension-belt element, in the form of, for example, a belt band, along a curved zone of the folding top covering. Both belt bands with scarcely any longitudinal elongation and resiliently stretchable belt bands are possible as the tension-belt element. So that the supporting forces could be transmitted via a belt band with hardly any longitudinal elongation, it is necessary to provide, on the belt band, a plurality of shaped pieces supported on the belt band under a compression-spring load, with the result that, with the folding top closed, these shaped pieces would bear against the folding-top fabric way of their shaping supporting contour under the expansion prestress provided by compression springs.
Preferably, however, a belt band is made of resiliently longitudinally stretchable material, since this requires no additional springs which need a corresponding constructional space.
If the folding-top covering contour to be stiffened changes considerably over the tensioning length, it is expedient if even the longitudinally stretchable belt band is equipped with a plurality of shaped pieces which are distributed over its length and the supporting contours of which are coordinated with the change in shape over the length.
In contrast, if the design of the folding-top covering contour to be stiffened is largely constant over the length, it is more expedient to attach the tension band with such a curvature that a wide side of the tension band itself bears supportively against the folding-top covering.
There are various possibilities, too, for the construction of the resiliently stretchable tension band.
Thus, the tension band can comprise a plurality of spring cords extending parallel to one another and made of helical tension springs, such as are known from expanders, in which case spring cords should be connected by means of a sheathing so as to form a wide band.
Alternatively, a shaped shell made of stretchable material or with stretchable length portions would also be used.
However, a prestressed belt band with a supporting structure made of an elastomeric material, such as rubber, is considered the most advantageous solution because of the small constructional space which it requires.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.